Isn't this the good old "naturalistic fallacy" though? Would you eat a poisonous mushroom because the poison is "natural"? You can at least wash some pesticides off.
I'm not a biologist but I'm sure there is a difference between crossing different varieties of peas versus introducing a non-pea (or maybe non-plant) gene into the pea DNA.
This is the exact same insecticide used by certified organic growers. Plant breeders have just engineered the plants to produce it in their leaves, not in the corn itself.
For thirty years objections have been raised, scientific research has been done disproving the objections. Yet Bt corn is still banned in a large part of Europe.
So they aren't really seperate.
"It's better for the environment" is a poor excuse when you have angry farmers yelling outside one door, and poor hungry people outside the other.
Europe might be a big enough market to be worth the R&D though - although it doesn't grow anywhere as much corn as we do.
Putting BT-Genes in plants also means using pesticides indiscriminately and precludes targeted pesticide use.
When a pesticide is widespread, insects develop resistance. At the moment, few insects have resistance to BT, because it is not continually in the environment in sufficiently high numbers.
So it works as an organic insecticide when needed.
Genetically engineer it into large numbers of plants, and in 30-40 years it is no longer effective.
Which means organic farmer no longer have the option of using it.
We can argue about the degree of overlap of course, but it's not clear cut. I believe our scientific understanding in this area is at best partial, and so minimal interference only where strong justification exists is preferable.
If you have a good explanation of the dangers of a particular action, then that’s sufficient to argue for caution—there’s no need for an additional principle, because you have an explanation about the dangers involved.
If you don’t have a good explanation of the dangers of a particular action, then you definitely don’t need a principle to tell you how cautious you ought to be. Presumably even when abiding by the precautionary principle one must estimate the plausibility of any hypothetical danger (to avoid universal hypothetical dangers of the form “there could be a wizard out there who has decided that they will kill us if we do X”), but developing good explanations for the plausibility of dangers is precisely the work mentioned in the previous paragraph that obviates the need for the precautionary principle.
I'm neither pro-pesticide nor anti-GMO but we should refrain ourselves from a blanket "GMO is natural, hence better than chemicals" statement.